linux-kernel - Re: [PATCH 07/10] i2c: Add driver for AD242x bus controller

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Date:   Thu, 12 Dec 2019 17:33:15 +0100
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Luca Ceresoli <luca@...aceresoli.net>
Cc:     Daniel Mack <daniel@...que.org>, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-clk@...r.kernel.org, mturquette@...libre.com,
        sboyd@...nel.org, robh+dt@...nel.org, broonie@...nel.org,
        lee.jones@...aro.org, lars@...afoo.de, pascal.huerst@...il.com
Subject: Re: [PATCH 07/10] i2c: Add driver for AD242x bus controller

Hi Luca,

thanks for the review!

> good, but I think there's a problem in this function. A "normal"
> master_xfer function issues a repeated start between one msg and the
> next one, at least in the typical case where all msgs have the same
> slave address. Your implementation breaks repeated start. At first sight
> we might need more complex code here to coalesce all consecutive msgs
> with the same address into a single i2c_transfer() call.

Note that it is by far the standard case that all messages in a transfer
have the same client address (99,999%?). But technically, this is not a
requirement and the repeated start on the bus is totally independent of
the addresses used. It is just a master wanting to send without being
interrupted by another master.

   Wolfram


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